1. Field of the Invention
The present invention relates to computing devices and to computer input devices.
2. State of the Art
Pen-based computers are known. As described in U.S. Pat. No. 5,457,476, incorporated herein by reference, a pen-based computer is typically a small, hand-held computer where the primary method for inputting data includes a "pen" or stylus. A pen-based computer system is commonly housed in a generally rectangular enclosure, and has a dual-function display assembly providing a viewing screen along one of the planar sides of the enclosure. The dual-function display assembly serves as both an input device and an output device. When operating as an input device, the display assembly senses the position of the tip of a stylus on the viewing screen and provides this positional information to the computer's central processing unit (CPU). Some display assemblies can also sense the pressure of the stylus on the screen to provide further information to the CPU. When operating as an output device, the display assembly presents computer-generated images on the screen.
The dual-function display assemblies of pen-based computer system permit users to operate the computer as computerized notepad. For example, graphical images can be input into the pen-based computer by merely moving the stylus on the surface of the screen. As the CPU senses the position and movement of the stylus, it generates a corresponding image on the screen to create the illusion that the stylus is drawing the image directly upon the screen, i.e., that the stylus is "inking" an image on the screen. With suitable recognition software, text and numeric information can also be entered into the pen-based computer system in a similar fashion.
Besides serving as a notepad, pen-based computers can provide a number of useful functions, such as provided in a personal organizer.
A problem with such pen-based computer systems has been the quick, accurate entry of text, especially passages of text longer than a name or phone number. To address this problem, some pen-based computer systems have been provided with optional compact keyboards. The problem with such keyboards, however, is that they defeat the original notion of the pen-based computer as being readily carried on one's person wherever one goes. If only the pen-based computer and not the keyboard is carried about, then the keyboard is unavailable for use the majority of the time. Planned, fixed usage of a keyboard, while marginally useful, does not effectively address the need for an improved method and device allowing for quick and easy input of text to a sub-notebook computing device.
An example of a particularly advantageous touch-sensitive computer input device is found in U.S. Pat. No. 5,194,862 issued Mar. 16, 1993 to Edwards (assigned to U.S. Philips Corporation), incorporated herein by reference. The patent discloses a touch sensor array built in a similar manner as a TFT active matrix liquid crystal display and which may be used as an overlay for the same. The touch sensor array offers comparable resolution as the liquid crystal display. U.S. Pat. No. 4,042,777 to Bequaert et al. (assigned to IBM) discloses a keyboard that uses chord keying. Mention is made of the possibility of realizing the key-board using touch keys rather than mechanical keys. The aforementioned patents, however, are silent regarding the quick and easy input of text to a sub-notebook computing device.